Historically overbased calcium sulfonates have been prepared by reacting a sulfonic acid with calcium hydroxide and carbon dioxide. This process generates a great amount of water. Removing the water extends the processing time, causes the overbased sulfonate to be viscous and generates water waste stream which must be treated before discharging to a sewer. These problems are ameliorated, if not eliminated, by utilizing calcium oxide and a less than stoichiometric amount of water in place of calcium hydroxide.
U.S. Pat. No. 3,384,587 (Holst et al., May 21, 1968) relates to a method of preparing hyperbasic calcium sulfonate lube oil concentrate useful as detergent dispersant additive in oils comprising forming a first reaction mixture of sulfonic acid or salt thereof, calcium hydroxide or calcium oxide and water, lower alkanol or lower alkoxy ethanol, and lubricating oil, sequentially injecting hydrogen sulfide and carbon dioxide under a hydrogen sulfide and carbon dioxide pressure of at least 10 p.s.i.g. and stripping off incidental water and oxygenated vehicle.
U.S. Pat. No. 3,471,403 (LeSuer et al., Oct. 7, 1969) discloses metal carboxylate complexes that are obtained by treating an oil-soluble carboxylic acid with a metal base in the presence of an acidic gas and an alcoholic promoter. The complexes are useful as detergent additives in fuels, oils, and other organic compositions and are especially useful in lubricating compositions.
U.S. Pat. No. 4,086,170 (De Clippeleir et al., Apr. 25, 1978) relates to calcium sulfonates and concentrated oily solutions thereof that are prepared by reacting a solution of alkylbenzene sulfonic acids with an excess of a calcium oxide having a medium or low activity towards water and with carbon dioxide. Oily solutions of overbased calcium sulfonate obtained from such a calcium oxide are limpid and filterable.
U.S. Pat. No. 4,604,219 (Whittle, Aug. 5, 1986) is directed to alkaline earth calcium sulfonates that are derived from natural or synthetic feedstocks or a mixture of both which can be overbased by introducing into a mixture comprising a neutral alkaline earth calcium sulfonate, a lower alcohol, a light hydrocarbon diluent carbon dioxide and water. The water is introduced continuously and at a uniform rate over 1-4 hours, preferably 1-3 hours into the heated mixture with carbon dioxide. Water is added in a molar ratio water/calcium oxide of 0.1 to 1.2 preferably 0.4 to 0.8. It has been found that both the water rate and amount are critical. It has been unexpectedly found that a superior product is formed by adding water continuously during carbonation rather than all charged in one or several increments at the beginning of the carbonation. In this reference, a high calcium sulfonate product with improved filterability and high clarity is formed with good lime utilization.
U.S. Pat. No. 4,775,490 (Nichols et al., Oct. 4, 1988) describes a process for overbasing a substrate comprising mixing the substrate, water, a phenol, a source of magnesium and a carbonating agent, wherein the water is retained throughout the overbasing reaction and provided further that the weight ratio of the water to the magnesium is in a 10:1 to 1:5 weight ratio, thereby obtaining a magnesium overbased substrate.
U.S. Pat. No. 4,954,272 (Jao, et al., Sep. 4, 1990) is directed to a process for producing an overbased oil soluble calcium sulfonate having a TBN of 325, said process comprising:
(a) diluting a neutral calcium sulfonate with a hydrocarbon solvent and a lower alkanol;
(b) adding to the diluted calcium sulfonate solution, CaO, Ca(OH).sub.2 and H.sub.2 O in molar ratios of CaO:Ca(OH).sub.2 of about 90:10 to about 20:80 and of H.sub.2 O:CaO of about 0.15:1 to about 0.30: 1;
(c) heating the sulfonate mixture to a temperature ranging from about 100.degree. F. to about 170.degree. F. under a pressure ranging from about 0 to about 50 p.s.i.g.;
(d) passing CO.sub.2 into the heated sulfonate mixture for a period of about 50 to out 200 minutes;
(c) adding a diluent oil to the CO.sub.2 treated sulfonate mixture;
(f) separating the solids from the liquid of the sulfonate mixture; and
(g) stripping the hydrocarbon solvent from the resulting overbased oil soluble sulfonate product having TBN of 325.
U.S. Pat. No. 5,259,966 (Burke, Jr., et al., Nov. 9, 1993) provides a process for preparing an overbased calcium salt, comprising mixing together:
(a) an oil-soluble acid material;
(b) a promoter comprising:
(i) an alcohol or alcohol mixture, and PA1 (ii) an inorganic calcium salt other than chloride which is soluble in the alcohol mixture of (i), or an acid or salt which forms said inorganic calcium salt when treated with a calcium base; and
(c) greater than 1 equivalent of a calcium base per equivalent of oil-soluble acid material.
U.S. Pat. No. 5,534,168 (Cleverley et al., Jul. 9, 1996) relates to the use of magnesium oxide of specified, low, reactivity in a process for the production of overbased magnesium sulfonates, together with the introduction of water and an alcohol, into the reaction mixture during carbonation, makes it possible to prepare high base number products which have very low post carbonation sediments and which can be purified by rapid filtration.